The exact measurement of how animals utilize space has not been carried out for many species. I wish to make exact determinations of the distances separating two conspecific individuals when they show agonistic behavior patterns. These measurements would be made on specimens which had been held under known density conditions, to assess the effects of population density on space-related behavior. Such observations would be made on species of crustacea with different social organization, in an attempt to see the effect of social system upon responses to density manipulations.